A pressure controller for use in an artificial respirator for supplying a gas to a patient requiring respiratory assistance is disclosed in, e.g., U.S. Pat. No. 6,644,313B2. This pressure controller (to be referred to as “the pressure controller of patent reference” hereinafter) disclosed in U.S. Pat. No. 6,644,313B2 includes a housing mechanism having an inspiratory gas inlet, inspiratory gas outlet and third vent hole. The pressure controller of patent reference further includes:
(a) a control valve placed in a substantially cylindrical valve housing of the housing mechanism so as to face a gas passage between the inspiratory gas inlet and inspiratory gas outlet,
(b) a coil spring for elastically biasing the control valve against a valve seat formed in the valve housing, and
(c) an adjustment manipulating cap to be rotated to adjust the elastic biasing force of the coil spring.
The adjustment manipulating cap is screwed into a threaded portion formed on the outer circumferential surface of the tubular portion of the valve housing. Also, a gas discharge hole is formed as the third vent hole in the tubular portion of the valve housing. The control valve opens or closes in accordance with the pressure of a gas flowing through the gas passage, and the amount of screw-tightening or screw-loosening of the adjustment manipulating cap with respect to the threaded portion. Therefore, the gas flowing through the gas passage partially flows outside from the gas discharge hole in accordance with this open/closure state. In addition, to prevent an unnecessary pivotal motion of the adjustment manipulating cap, a pivotal-motion-preventing locking cap is detachably fitted on the cylindrical portion so as to cover the adjustment manipulating cap.
In the pressure controller of patent reference configured as described above, however, the adjustment manipulating cap must be covered with the pivotal-motion-preventing locking cap in order to prevent an unnecessary pivotal motion of the adjustment manipulating cap when, e.g., an operator or the like touches the cap with fingers. Also, to tighten or loosen the adjustment manipulating cap, the pivotal-motion-preventing locking cap must be removed from the adjustment manipulating cap. This increases the number of parts because the pivotal-motion-preventing locking cap is additionally necessary. In addition, the adjustment manipulating cap must be pivoted after the pivotal-motion-preventing locking cap is removed, and the pivotal-motion-preventing locking cap must be reattached after this pivotal motion. This complicates the pivoting operation of the adjustment manipulating cap as a whole. Also, the adjustment manipulating cap may unnecessarily pivot when removing and attaching the pivotal-motion-preventing locking cap. Furthermore, an operator may lose the pivotal-motion-preventing locking cap or may forget to attach it. Accordingly, the pressure controller of patent reference has the problem in reliably preventing an unnecessary pivotal motion of the adjustment manipulating cap.